1. Field of the Invention
This invention relates to paper sheeters and delivery equipment used in a high speed web printing press operation, particularly to such equipment used for handling lightweight and recycled paper stocks which are relatively limp. The sheets must be decelerated after leaving the high speed section of the apparatus.
2. Description of the Related Art
The following patents describe various types of sheet feeding equipment:
______________________________________ Patent Number Inventor Date ______________________________________ 2,261,972 Matthews 1941 3,178,174 Schneider 1965 3,502,321 McWhorter 1970 3,507,489 Wilshin, et al 1970 3,994,221 Littleton 1976 4,682,767 Littleton 1987 U.K. 1,158,844 E. C. H. Will 1969 ______________________________________
Matthews '972 describes upper and lower rollers 19 and 39, best seen in FIG. 8 which deflect the incoming sheets 56 to provide a soft means for stopping the high speed travel of the sheet. This apparatus worked well for sheet stock having good body, but jams when lightweight or recycled paper sheets are fed through.
Schneider '174 obtains a braking effect in his apparatus by means of a compressed air nozzle, or a press-down component, and suction device or brake bands which act together on the rear end of the sheet. McWhorter '321 describes a collating machine which transfers sheets from a high speed section to a low speed section. Braking of the overlapped, stacked sheets is effected by a series of nip assemblies which include a back-up roller and an upper roller and a belt nip assembly. When lightweight or limp-bodied paper (recycled paper) is fed through such a slow down system, the trailing edges of the sheets tend to curve up and jam.
British Patent 1,158,844 shows an intermittently operated belt-retarder which travels more slowly than the conveyor belt and the rear end of each incoming sheet is pressed and retarded by a segment on a rotor. Again, the system does not work as well with limp-bodied sheets because they tend to curl at the outside trailing edges, and interfere with the next incoming sheet.
Wilshin et al '489 describes a slow down system for a sheet feeding apparatus which employs a reciprocating roller which is synchronized to only contact the incoming sheets at their trailing edge as the trailing portion of each sheet is passing the roller. This system was satisfactory at lower speeds for sheets having body, but limp or lightweight sheets tend to curl at the outside trailing edges, and the leading edge of the next incoming sheet tends to jam against the rear of the first sheet.
Littleton '221 describes a slow down system incorporating rotary snubbers (knockdown arms) which cooperate with squaring rollers to insure shingling of the sheets as they are decelerated on the second, lower speed conveyor. The rotary snubbers act on the middle of trailing portion of the sheets so when limp-bodied sheets are handled, the outside trailing portions tend to curl and jam against the next incoming sheet.
Littleton '767 describes a snubber means which cooperates with a deck plate to slow the sheets coming from the high speed section of a sheet handling system. The snubber contacts the trailing portion of each incoming sheet. The same problem occurs with this system when limp-bodied sheets are handled. The outside trailing portions of the sheets tend to curl up and cause the next incoming sheet to jam.